system-config-language-1.3.2-3.fc10.noarch seems to use the firstboot directory structure as well, but to be able to do that without a package requirement:
| [tim@lockfix ~/Desktop/Agenda]$ rpm -qf /usr/share/firstboot/
| system-config-language-1.3.2-3.fc10.noarch
| firstboot-1.102-1.fc10.i386
| [tim@lockfix ~/Desktop/Agenda]$
It would be really nice if the dependency of system-config-keyboard on firstboot could be lost as firstboot draws in metacity and other packages in return.